2-Amino-6-fluoronicotinic acids and derivatives thereof and methods of herbicidal use

ABSTRACT

Novel 2-amino-6-fluoronicotinic acids, amides and esters, herbicidal compositions containing these compounds and methods of using such compounds for the control of wild oats in wheat.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates (a) to novel 2-amino-6-fluoronicotinic acids,amides and esters thereof, (b) to herbicidal compositions of such novelcompounds and (c) to preemergent and postemergent methods of using suchcompounds for the control of grassy weeds in non-crop areas as well asin the presence of many valuable crops.

2. Description of the Prior Art

U.S. Pat. No. 2,516,830 issued July 25, 1950 discloses various nicotinicacid compounds such as 5-fluoronicotinic acid and 5-fluoronicotinamideand their use as antimetabolites against streptococci.

Chemical Abstracts 43:9069b discloses the synthesis of certainalpha-halogenated pyridine compounds, including 6-fluoronicotinamide andChemical Abstracts 58:4836a discloses the inhibition of bacteria by5-fluoronicotinic acid.

SUMMARY OF THE INVENTION

The present invention is directed to novel 2-amino-6-fluoronicotinicacids, amides and esters having the formula ##STR1## wherein Rrepresents hydrogen or methyl; R' represents CN or ##STR2## wherein Xrepresents SAr, OR", NH₂ or OM; Ar represents ##STR3## R" represents H,C₁ -C₄ alkyl, ##STR4## alkenyl, alkynyl, hydroxyalkyl, aminoalkyl oralkoxyalkyl; R'" represents H or C₁ -C₄ alkyl; M represents alkalimetal, ammonia, alkanol amine, or mono or dialkylamine and Z representshydrogen, Cl, Br, F, CH₃, OCH₃ or CF₃.

Preferred compounds are 2-amino-6-fluoronicotinic acid, ethyl2-amino-6-fluoro-3-pyridinecarboxylate, benzyl2-amino-6-fluoro-3-pyridinecarboxylate, β-methoxyethyl2-amino-6-fluoro-3-pyridinecarboxylate, and 3-fluorobenzyl2-amino-6-fluoro-3-pyridinecarboxylate.

The foregoing compounds, preferably formulated as liquid compositions,are used according to the methods of the invention for the control ofundesired vegetation, particularly grassy weeds, and most particularlywild oats, advantageously in the presence of many valuable crops. Someof the compounds are more useful in postemergent applications while theothers are useful in preemergent operations as well.

The compounds of the above formula, hereinafter referred to forconvenience as "active ingredients", have been found to be especiallyactive as herbicides for the control of undesired vegetation, forexample, grassy or graminaceous weeds. Accordingly, the presentinvention also encompasses compositions containing one or more activeingredients as well as preemergent and postemergent methods ofcontrolling undesired plant growth, especially in the presence ofvaluable crops, particularly wheat and broadleaf crops. Such methodscomprise applying a herbicidally-effective amount of one or more activeingredients to the locus of the undesired plants, that is, the seeds,foliage, stems and roots or other parts of the growing plants or soil inwhich the plants are growing or may be found.

DETAILED DESCRIPTION OF THE INVENTION

The term "herbicide" is used herein to mean an active ingredient whichcontrols or adversely modifies the growth of plants because ofphytotoxic or other effects substantial enough to seriously retard thegrowth of the plant or to further damage the plant sufficiently to killit.

By "growth controlling" or "herbicidally-effective" amount is meant anamount of active ingredient which causes a modifying effect and includesdeviations from natural development, killing, regulation, desiccation,retardation, and the like.

The term "plants" is meant to include germinant seeds, emergingseedlings, and established vegetation.

The term "C₁ -C₄ alkyl, alkenyl or alkynyl" refers to groups which maybe straight or branched chain and contain from 1 to 4 carbon atoms. Theterms "alkoxyalkyl, hydroxyalkyl and aminoalkyl" refer to groups havingfrom 1 to 4 carbon atoms in the alkyl and/or alkoxy portion of themolecule.

The active ingredients of the present invention are generally oils orcrystalline solids at ambient temperatures.

The compounds of the present invention may be prepared from theappropriate ester of 2,6-difluoropyridine-3-carboxylic acid by addingthe ester to a vigorously stirred solution of anhydrous ammonia (≧3equivalents) in formamide. Stirring is continued at room temperatureuntil thin layer chromatography (silica gel, 7:3 hexane-acetone orsilica gel, 9:1 chloroform-methanol) indicates the absence of thestarting difluoro compound (30 minutes--16 hours). During this periodthe starting difluoro compound dissolves and then usually a solidseparates from the solution. When the reaction is complete, the mixtureis poured into water (1-2 liters) whereupon a solid usually separates.This may be extracted with a suitable solvent, such as ethyl acetate,chloroform, or ether (this is necessary if no solid separates) orfiltered and air dried. If the material is extracted with a solvent, theorganic phase is dried (MgSO₄) and the solvent evaporated. In all casesthe material obtained from the reaction is a mixture of the desired2-amino-6-fluoropyridine-3-carboxylic acid ester and its isomer6-amino-2-fluoropyridine-3-carboxylic acid ester. Separation of thesetwo isomers may be effected in one of two ways: (1) The mixture issubjected to continuous extraction via a Soxhlet apparatus using eitherhexane or methyl cyclohexane as the solvent. This extracts the desired2-amino-6-fluoro isomer leaving the isomeric 6-amino-2-fluoropyridine-3-carboxylic acid ester as an undissolved solid.Recrystallization from appropriate solvents completes the purificationprocess. (2) The mixture may be separated via preparative high pressureliquid chromatography on silica gel using an appropriate combination ofacetone in hexane as an eluent (5-30% acetone in hexane). The desired2-amino-6-fluoropyridine-3-carboxylic acid ester always elutes firstfrom the column. Recrystallization from an appropriate solvent completesthe purification process.

EXAMPLE 1 2-Amino-6-fluoropyridine-3-carboxylic acid, n-butyl ester

To a mechanically stirred solution of ammonia (14 grams (g)) informamide (300 milliliter (ml)) was added all at once butyl2,6-difluoropyridine-3-carboxylate (29 g, 0.135 mole). The resultingmixture was stirred overnight at room temperature. The mixture was thenpoured into water (1500 ml) and the product was filtered. After washingwith several portions of water, the solid was dissolved in chloroform,dried (MgSO₄) and the solvent evaporated. The resulting solid (26 g,m.p.=84°-120° C.) was separated via preparative high pressure liquidchromatography (8:2 hexane-acetone) to give first the desired butyl2-amino-6-fluoropyridine-3-carboxylate (10 g) which afterrecrystallization from hexane had a m.p.=88.5°-90.5° C. Eluting secondwas the isomeric butyl 6-amino-2-fluoropyridine-3-carboxylate (9 g)which after recrystallization from toluene had a m.p.=132.5°-134° C.

EXAMPLE 2 2-Amino-6-fluoropyridine-3-carboxylic acid, benzyl ester

To a stirred solution of ammonia (15 g) in formamide (250 ml) was addedall at once benzyl 2,6-difluoropyridine-3-carboxylate (20 g, 0.08 mole).The mixture slowly became homogeneous, then a solid began to separate.After two hours, the mixture was poured into water (1000 ml) and thesolid filtered. The solid was washed with several portions of water thenair dried. Continuous extraction for one hour via a Soxhlet extractionapparatus using hexane as the solvent gave, after concentrating to 250ml and cooling, 6.0 g (30%) of the desired benzyl2-amino-6-fluoropyridine-3-carboxylate: m.p.=92°-94° C. The hexaneinsoluble material was recrystallized from a small volume of acetone togive 5.5 g (28%) of the isomeric benzyl6-amino-2-fluoropyridine-3-carboxylate: m.p.=157.5°-159.5° C.

EXAMPLE 3 2-Amino-6-fluoropyridine-3-carboxylic acid

A solution of benzyl 2-amino-6-fluoropyridine-3-carboxylate (2.0 g,0.008 mole) in ethanol (250 ml) containing 5 percent Palladium oncharcoal was shaken in a hydrogen atmosphere (50 psi was the initialpressure) using a Paar apparatus. Hydrogen uptake ceased after 10-15minutes. After purging the hydrogen from the system, the catalyst wasremoved by filtration, and the solvent evaporated to give 1.2 g (94percent) of the desired acid. Recrystallization from water gave ananalytical sample: m.p.=205-214 decompose.

Employing the above procedures, the following compounds were prepared:

    __________________________________________________________________________     ##STR5##                                                                                            Analysis                                               X               M.P. °C.                                                                           C   H   N                                         __________________________________________________________________________     ##STR6##       155-158                                                                              Theory Found                                                                       52.56 52.65                                                                       2.94 2.96                                                                         30.65 30.24                               NH.sub.2        198-200                                                                              Theory                                                                             46.45                                                                             3.90                                                                              27.09                                                            Found                                                                              46.37                                                                             3.74                                                                              27.09                                     OCH.sub.2 CH.sub.3                                                                            127-128                                                                              Theory                                                                             52.19                                                                             4.89                                                                              15.21                                                            Found                                                                              52.16                                                                             5.01                                                                              15.05                                     OCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3                                                          88.5-90.5                                                                            Theory                                                                             56.59                                                                             6.17                                                                              13.20                                                            Found                                                                              56.67                                                                             6.19                                                                              13.17                                     OH              205-214                                                                              Theory                                                                             46.16                                                                             3.23                                                                              17.95                                                     dec.   Found                                                                              46.18                                                                             3.41                                                                              17.67                                     OCH.sub.2 Ph    92-94  Theory                                                                             63.41                                                                             4.50                                                                              11.38                                                            Found                                                                              63.20                                                                             4.42                                                                              11.41                                     OCH.sub.2 CH.sub.3 [NH.sub.2 = N(CH.sub.3).sub.2 ]                                            R.I. 1.5260                                                                          Theory                                                                             56.59                                                                             6.17                                                                              13.20                                                            Found                                                                              56.51                                                                             6.67                                                                              13.21                                     OCH.sub.2 CH.sub.3 [NH.sub.2 = NHCH.sub.3 ]                                                   62.5-65                                                                              Theory                                                                             54.54                                                                             5.60                                                                              14.14                                                            Found                                                                              54.09                                                                             5.60                                                                              13.94                                     OCH(CH.sub.3).sub.2                                                                           88-90  Theory                                                                             54.54                                                                             5.60                                                                              14.14                                                            Found                                                                              54.43                                                                             5.57                                                                              14.08                                     OCH.sub.3       128-131                                                                              Theory                                                                             49.41                                                                             4.15                                                                              16.47                                                            Found                                                                              49.06                                                                             4.14                                                                              16.13                                      ##STR7##       141-145                                                                              Theory Found                                                                       55.62 55.63                                                                       3.59 3.61                                                                          9.98 9.98                                 ##STR8##         122-123.5                                                                          Theory Found                                                                       64.60 64.28                                                                       5.03 4.93                                                                         10.77 10.66                                ##STR9##       139-141                                                                              Theory Found                                                                       60.86 60.98                                                                       4.74 4.82                                                                         10.14 10.08                               OCH.sub.2 CH.sub.2 OCH.sub. 3                                                                 73-76  Theory                                                                             50.46                                                                             5.18                                                                              13.08                                                            Found                                                                              50.44                                                                             5.17                                                                              13.26                                      ##STR10##      129-131                                                                              Theory Found                                                                       59.09 58.85                                                                       3.81 3.82                                                                         10.60 10.56                               OCH.sub.2 CCH   128-130                                                                              Theory                                                                             55.67                                                                             3.63                                                                              14.43                                                            Found                                                                              55.52                                                                             3.77                                                                              14.59                                     OCH.sub.2 CHCH.sub.2                                                                          71-73  Theory                                                                             55.10                                                                             4.62                                                                              14.28                                                            Found                                                                              54.92                                                                             4.73                                                                              14.53                                      ##STR11##        122-124.5                                                                          Theory Found                                                                       55.62 55.29                                                                       3.59 3.58                                                                          9.98 9.98                                 ##STR12##      111-113                                                                              Theory Found                                                                       59.09 58.61                                                                       3.81 3.88                                                                         10.60 10.51                                ##STR13##        115-117.5                                                                          Structure confirmed by NMR                              ##STR14##      123.5-126                                                                            Theory Found                                                                       53.51 53.29                                                                       3.21  3.28                                                                         8.92 8.87                                OCH.sub.2 CH.sub.2 N(CH.sub.3).sub.2                                                          35-41  Structure confirmed by NMR                             OCH.sub.2 CH.sub.2 OCH.sub.2 Ph                                                                 64-65.5                                                                            Theory                                                                             62.06                                                                             5.21                                                                               9.65                                                            Found                                                                              61.90                                                                             5.13                                                                               9.72                                     OCH.sub.2 CH.sub.2 OH                                                                         116-119                                                                              Theory                                                                             48.00                                                                             4.53                                                                              14.00                                                            Found                                                                              47.95                                                                             4.49                                                                              13.89                                      ##STR15##      88-96  Theory Found                                                                       55.93 56.19                                                                       3.84 3.98                                                                         11.86 11.47                                ##STR16##      153.5-155.5                                                                          Theory Found                                                                       63.13 63.54                                                                       5.63 5.91                                                                          9.20 9.09                                 ##STR17##        106-107.5                                                                          Theory Found                                                                       49.59 49.61                                                                        4.58 4.58                                                                        11.57 11.62                               __________________________________________________________________________

The compounds of the present invention have been found to beparticularly suitable for use in methods for the pre and postemergentcontrol of grassy weeds. The active ingredients of the present inventionhave been found to have advantage over prior art compounds in thecontrol of wild oats. In addition, the present compounds aresufficiently tolerant towards most broad leafed crops and grassy crops,such as wheat, to contemplate control of grassy weeds therein atsubstantially commercially practicable levels, particularly so with thepreferred compounds.

For all such uses, unmodified active ingredients of the presentinvention can be employed. However, the present invention embraces theuse of a herbicidally-effective amount of the active ingredients incomposition form with an inert material known in the art as anagricultural adjuvant or carrier in solid or liquid form. Such adjuvantsor carriers must not be phytotoxic to valuable crops particularly at theconcentration employed in applying the composition in attemptingselective weed control in the presence of crops. If weed control isdesired in the absence of crops, it is generally sufficient to employadjuvants or carriers which do not leave a persistent phytotoxicresidue.

Thus, for example, an active ingredient can be dispersed on afinely-divided solid and employed therein as a dust. Also, the activeingredients, as liquid or solid compositions comprising one or more ofthe active ingredients, can be dispersed in water, typically with aid ofa wetting agent, and the resulting aqueous dispersion employed as aspray. In other procedures, the active ingredients can be employed as aconstituent of organic liquid compositions, oil-in-water andwater-in-oil emulsions or dispersions, with or without the addition ofwetting, dispersing, or emulsifying agents.

Suitable adjuvants of the foregoing type are well known to those skilledin the art. The methods of applying the solid or liquid herbicidalformulations similarly are well known to the skilled artisan.

The active ingredients can also be applied as aerosols, e.g., bydispersing them by means of a compressed gas such as one of thehydrocarbon successors to the fluorocarbons.

The active ingredients of the present invention can also be applied withsolid adjuvants or carriers such as talc, pyrophyllite, synthetic finesilica, attapulgus clay, kieselguhr, chalk, diatomaceous earth, lime,calcium carbonate, bentonite, Fuller's earth, cotton seed hulls, wheatflour, soybean flour, pumice, tripoli, wood flour, walnut shell flour,redwood flour and lignin.

As stated, it is frequently desirable to incorporate a surface-activeagent in the compositions of the present invention. Such surface-activeor wetting agents are advantageously employed in both the solid andliquid compositions. The surface-active agent can be anionic, cationicor nonionic in character.

Typical classes of surface-active agents include alkyl sulfonate salts,alkylaryl sulfonate salts, alkylaryl polyether alcohols, fatty acidesters of polyhydric alcohols and the alkylene oxide addition productsof such esters, and addition products of long-chain mercaptans andalkylene oxides. Typical examples of such surface-active agents includethe sodium alkylbenzene sulfonates having 10 to 18 carbon atoms in thealkyl group, alkyl phenol ethylene oxide condensation products, e.g.,p-isooctylphenol condensed with 20 ethylene oxide units, soaps, e.g.,sodium stearate and potassium oleate, sodium salt of propylnaphthalenesulfonic acid, di(2-ethylhexyl)ester of sodium sulfosuccinic acid,sodium lauryl sulfate, sodium decyl sulfonate, sodium salt of thesulfonated monoglyceride of coconut fatty acids, sorbitan sesquioleate,lauryl trimethyl ammonium chloride, octadecyl trimethyl ammoniumchloride, polyethylene glycol lauryl ether, polyethylene glycol estersof fatty acids and rosin acids, e.g., Ethofat 7 and 13, sodiumN-methyl-N-oleyl taurate, Turkey Red Oil, sodium dibutylnaphthalenesulfonate, sodium lignin sulfonate, polyethylene glycol stearate, sodiumdodecyl benzene sulfonate, tertiary dodecyl polyethylene glycolthioether (nonionic 218), long-chain ethylene oxide-propylene oxidecondensation products, e.g., Pluronic 61 (molecular weight about 1000),polyethylene glycol ester of tall oil acids, sodiumoctophenoxyethoxyethyl sulfate, tris(polyoxyethylene)sorbitanmonostearate (Tween 60), and sodium dihexylsulfosuccinate.

The concentration of the active ingredients in solid or liquidcompositions generally is from about 0.003 to about 95 percent by weightor more. Concentrations from about 0.05 to about 50 percent by weightare often employed. In compositions to be employed as concentrates, theactive ingredient can be present in a concentration from about 5 toabout 98 weight percent, preferably 15-50 weight percent. The activeingredient compositions can also contain other compatible additaments,for example, phytotoxicants, plant growth regulants, pesticides and thelike and can be formulated with solid particulate fertilizer carrierssuch as ammonium nitrate, urea and the like.

The present compositions can be applied by the use of power dusters,boom and hand sprayers, spray dusters, by addition to irrigation water,and by other conventional means. The compositions can also be appliedfrom airplanes as a dust or spray since the active ingredients areeffective at very low application rates.

The active ingredients of the present invention have been found topossess desirable herbicidal activity in general against grassy weedssuch as foxtail, barnyard grass, wild oats and crabgrass in preemergentoperations and also against the same grasses in postemergent operations.The active ingredients of the present invention have been found topossess particularly desirable herbicidal activity against wild oats inpostemergent operations with selectivity to wheat and broadleaf crops.

The exact rate to be applied is dependent not only on a specific activeingredient being applied, but also on a particular action desired (e.g.,general or selective control), the plant species to be modified and thestage of growth thereof as well as the part of the plant to be contactedwith the toxic active ingredient. Thus, it is to be understood that allof the active ingredients of the present invention and compositionscontaining the same may not be equally effective at similarconcentrations or against the same plant species. In non-selectivepreemergence and foliar treatments, the active ingredients of theinvention are usually applied at an approximate rate of from about 0.5to about 10 pounds/acre, but lower or higher rates may be appropriate insome cases, such as 0.10 to about 20 pounds/acre or more. In preemergentoperations for selective uses, a dosage of about 0.10 to about 20pounds/acre or more is generally applicable, a rate of 0.25 to 10pounds/acre being preferred and about 0.5 to about 5 pounds/acre beingmost preferred.

In postemergent operations a dosage of about 0.10 to about 20pounds/acre or more is generally applicable, although not all compoundsare equally effective and some weeds are more difficult to control. Adosage rate in the range of about 0.25 to about 5.0 pounds/acre ispreferred in selective postemergent control of annual grassy weeds.

In view of the foregoing and the following disclosures, one skilled inthe art can readily determine the optimum rate to be applied in anyparticular case.

In representative operations, each compound to be utilized in a seriesof tests is dissolved in acetone to one half of the final volume (twicethe final concentration) to be used and the acetone solution in eachcase is admixed with an equal volume of water containing 0.1 percent byweight of Tween-20 surface active material (Tween-20is a trademark ofAtlas Chemical Company). Each compound is selected from a groupconsisting of compounds according to the invention. The compositions,generally in the nature of an emulsion, were employed to treat separaterespective seed beds of sandy loam soil of good nutrient content whereineach seed bed contained separate groups of good viable seeds, each groupbeing of one of a predetermined plant species. The various beds werepositioned side by side and exposed to substantially identicalconditions of temperature and light. Each bed was maintained so as toprevent any interaction with test compounds in different seed beds. Eachseed bed was treated with one of the compositions as a soil drenchapplied at predetermined rates to deposit a predetermined amount of agiven test compound uniformly throughout the surface of the bed. Thecompositions were applied to the seed beds so that different seed bedsof a given plant species were treated with one of each of the testcompounds. Another seed bed was treated only with water to serve as acontrol. After treatment, the seed beds were maintained for two weeksunder greenhouse conditions conducive for good plant growth and wateredas necessary. The specific plant species, test compound and dosage andthe percent preemergent control obtained are set forth in Table I below.Control refers to the reduction in growth compared to the observedresults of the same species.

                                      TABLE I                                     __________________________________________________________________________    PREEMERGENCE CONTROL OF PLANT SPECIES                                          ##STR18##                                                                                               % Control                                          Compound Tested     Dosage in     Barnyard                                                                           Crab-   Johnson                                                                            Wild-                     R   R'   X          Pounds/Acre                                                                          Rice                                                                             Wheat                                                                             Grass                                                                              Grass                                                                             Foxtail                                                                           Grass                                                                              Oats                      __________________________________________________________________________    H.sub.2                                                                            ##STR19##                                                                          ##STR20## 4 2 1 0.5 0.25                                                                       90 90 30 0 0                                                                     90 20 0 0 0                                                                       90 95 30 0 0                                                                       90 70 30 0 0                                                                      80 30 0  0 0                                                                      95 40 20 0 0                                                                       98 95 80 60 0             H.sub.2                                                                            ##STR21##                                                                         OH         4 2 1 0.5 0.25                                                                       100 100 30 0 0                                                                   90 100 40 0 0                                                                     98 70 60 50 0                                                                      100 100 0 0 0                                                                     30 40 0 0 0                                                                       70 70 50 0 0                                                                       100 98 40 30 0            H.sub.2                                                                            ##STR22##                                                                          ##STR23## 4 2 1 0.5 0.25                                                                       0 0 0 0 0                                                                        0 0 0 0 0                                                                         70 0 0  0 0                                                                        30 0 0 0 0                                                                        0 0 0 0 0                                                                         90 60 0 0 0                                                                        80 90 40 30 0             H.sub.2                                                                            ##STR24##                                                                          ##STR25## 4 2 1 0.5 0.25                                                                       0 0 0 0 0                                                                        30 0 0 0 0                                                                        0 0 0 0 0                                                                          0 0 0 0 0                                                                         0 0 0 0 0                                                                         0 0 0 0 0                                                                          30 0 0 0 0                HCH.sub.3                                                                          ##STR26##                                                                         OCH.sub.2 CH.sub.3                                                                       4 2 1 0.5 0.25                                                                       0 0 0 0  0                                                                       0 0 0 0 0                                                                         0 0 0 0 0                                                                          0 0 0 0 0                                                                         0 0 0 0 0                                                                         0 0 0 0 0                                                                          100 0 0 0 0               H.sub.2                                                                            ##STR27##                                                                         OCH.sub.2 CH.sub.2 OCH.sub.3                                                             4 2 1 0.5 0.25                                                                       100 100 0 0 0                                                                    80 20 0 0 0                                                                       100 98 30 0 0                                                                      100 80 20 0 0                                                                     20 0 0 0 0                                                                        30 20 0 0 0                                                                        95 95 60 30 0             H.sub.2                                                                            ##STR28##                                                                          ##STR29## 4 2 1 0.5 0.25                                                                       90 70 20 0 0                                                                     0 0 0 0 0                                                                         90 70 30 0 0                                                                       40 0 0 0 0                                                                        0 0 0 0 0                                                                         50 0 0 0 0                                                                         98 95 80 50 0             __________________________________________________________________________

On repeating the foregoing test procedures using other substituted2-amino-6-fluoronicotinic acids of the invention and derivatives hereinembraced substantially the same preemergent herbicidal results areobtained.

So as to illustrate clearly the phytotoxic properties of the variousactive ingredients of the present invention applied postemergently, agroup of controlled greenhouse experiments is described below.

Various species of plants were planted in beds of good agricultural soilin a greenhouse. After the plants had emerged and grown to a height ofabout 2-6 inches a portion of the plants were sprayed with an aqueousmixture, made by mixing a selected active ingredient and emulsifier ordispersant with about 1:1 water-acetone, employing sufficient amounts ofthe treating composition to provide application rates of 4000 parts permillion (ppm) or about 10 pounds per acre and in some cases at lowerrates. Other plants were left untreated to serve as controls.

After a period of 2-3 weeks, the effect of the respective testingredients used on respective groups of plants was evaluated by acomparison with the control groups of the plants. The results aretabulated below in Table II.

                                      TABLE II                                    __________________________________________________________________________    POSTEMERGENCE CONTROL OF PLANT SPECIES                                         ##STR30##                                                                                            % Control                                             Compound Tested                Barnyard                                                                           Crab-   Johnson                                                                            Wild-                        R R'   X        Dosage (PPM)                                                                          Rice                                                                             Wheat                                                                             Grass                                                                              grass                                                                             Foxtail                                                                           Grass                                                                              Oats                         __________________________________________________________________________    H.sub.2                                                                          ##STR31##                                                                          ##STR32##                                                                             2000 1000 500 250 125 62.5                                                            50 0 0 0 0 0                                                                     100 98 90 70 40 0                                                                 100 100 80 40 20 0                                                                 100 100 100 40 30 0                                                               0 0 0 0 0 0                                                                       30 0 0 0 0 0                                                                       100 100 100 97 95 30         H.sub.2                                                                          ##STR33##                                                                         OH       2000 1000 500 250 125 62.5                                                            80 70 30 0 0 0                                                                   90 80 95 80 70 40                                                                 100 100 100 98 20 0                                                                100 100 95 40 30 0                                                                80 30 20 0 0 0                                                                    98 40 30 0 0 0                                                                     100 100 100 95 97 50         H.sub.2                                                                          ##STR34##                                                                          ##STR35##                                                                             2000 1000 500 250 125 62.5                                                             30 0 0 0 0 0                                                                    0 0 0 0 0 0                                                                       100 80 30 0 0 0                                                                    100 100 20 0 0 0                                                                  30 0 0 0 0 0                                                                      0 0 0 0 0 0                                                                        98 95 90 90 90 70            __________________________________________________________________________

In postemergent operations carried out as described above, ethyl2-amino-6-fluoro-3-pyridinecarboxylate gave 20 percent control offoxtail and Johnson grass and 95 percent control of wild oats at 500ppm. There was no control of rice, wheat, barnyard grass or crabgrass.Similarly, at 2000 ppm, p-fluorobenzyl2-amino-6-fluoro-3-pyridinecarboxylate gave 30 percent control of rice,20 percent control of crabgrass and 60 percent control of wild oats withno control of wheat, barnyard grass, foxtail or Johnson grass while thecorresponding p-chlorobenzyl compound gave 10 percent control of rice,20 percent control of wheat and 90 percent control of wild oats. At 1000ppm isopropyl 2-amino-6-fluoro-3-pyridine carboxylate gave 30 percentcontrol of barnyard grass and 95 percent control of wild oats with nocontrol of the other plant species above;ethyl-2-methylamino-6-fluoro-3-pyridinecarboxylate gave 20 percentcontrol of rice and 80 percent control of wild oats and methyl2-amino-6-fluoro-3-pyridinecarboxylate gave 20 percent control ofbarnyard grass and 100 percent control of wild oats.

In further postemergent operationsp-methylbenzyl-2-amino-6-fluoro-3-pyridinecarboxylate, at 2000 ppm, gave20 percent control of barnyard grass and Johnson grass, 30 percentcontrol of wheat and crabgrass and 95 percent control of wild oats;p-methoxybenzyl 2-amino-6-fluoro-3-pyridinecarboxylate gave 20 percentcontrol of wheat and barnyard grass, 30 percent control of crabgrass, 70percent control of Johnson grass and 90 percent control of wild oats;propargyl 2-amino-6-fluoro-3-pyridinecarboxylate gave 100 percentcontrol of wild oats with no control of the other plant species and2-amino-6-fluoro nicotinamide, at 500 ppm, gave 100 percent control ofcrabgrass with no control of the other plant species.

What is claimed is:
 1. A compound having the formula ##STR36## wherein Rrepresents hydrogen or methyl; R' represents ##STR37## wherein Xrepresents OR", or OM; R" represents H, C₁ -C₄ alkyl, alkoxyalkyl or##STR38## M represents alkali metal, ammonia, alkanol amine, or mono ordialkylamine and Z represents hydrogen, Cl, Br, F, CH₃, OCH₃ or CF₃wherein each alkyl, alkoxy or alkanol group contains 1-4 carbon atoms.2. Compound of claim 1 wherein R is hydrogen and R' is ##STR39## whereinX is OH, ethoxy or OR" wherein R" is benzyl.
 3. Compound of claim 2which is 2-amino-6-fluoronicotinic acid.
 4. Compound of claim 2 which isethyl 2-amino-6-fluoro-3-pyridinecarboxylate.
 5. Compound of claim 2which is benzyl 2-amino-6-fluoro-3-pyridinecarboxylate.
 6. Compound ofclaim 1 which is 3-fluorobenzyl 2-amino-6-fluoro-3-pyridinecarboxylate.7. Compound of claim 1 which is beta-methoxyethyl2-amino-6-fluoro-3-pyridinecarboxylate.
 8. An herbicidal compositioncomprising an inert carrier and an herbicidally effective amount of acompound having the formula ##STR40## wherein R represents hydrogen ormethyl; R' represents ##STR41## wherein X represents OR", or OM; R"represents H, C₁ -C₄ alkyl, alkoxyalkyl or ##STR42## M represents alkalimetal, ammonia, alkanol amine, or mono or dialkylamine and Z representshydrogen, Cl, Br, F, CH₃, OCH₃ or CF₃ wherein each alkyl, alkoxy, oralkanol group contains 1-4 carbon atoms.
 9. Composition of claim 8wherein the compound is 2-amino-6-fluoronicotinic acid.
 10. Compositionof claim 8 wherein the compound is ethyl2-amino-6-fluoro-3-pyridinecarboxylate.
 11. Composition of claim 8wherein the compound is benzyl 2-amino-6-fluoro-3-pyridinecarboxylate.12. Composition of claim 8 wherein the compound is 3-fluorobenzyl2-amino-6-fluoro-3-pyridine carboxylate.
 13. Composition of claim 8wherein the compound is β-methoxyethyl2-amino-6-fluoro-3-pyridinecarboxylate.
 14. Method for selectivelycontrolling wild oats in grassy crops such as wheat which comprisesapplying to said grassy crops, or to the soil in which said grassy cropsare to be grown, an herbicidally effective amount of a compound havingthe formula ##STR43## wherein R represents hydrogen or methyl; R'represents ##STR44## wherein X represents OR", or OM; R" represents H,C₁ -C₄ alkyl, alkoxyalkyl or ##STR45## M represents alkali metal,ammonia, alkanol amine, or mono or dialkylamine and Z representshydrogen, Cl, Br, F, CH₃, OCH₃ or CF₃ wherein each alkyl, alkoxy oralkanol group contains 1-4 carbon atoms.
 15. Method of claim 14 whereinthe compound is 2-amino-6-fluoronicotinic acid.
 16. Method of claim 14wherein the compound is ethyl 2-amino-6-fluoro-3-pyridinecarboxylate.17. Method of claim 14 wherein the compound is benzyl2-amino-6-fluoro-3-pyridinecarboxylate.
 18. Method of claim 14 whereinthe compound is 3-fluorobenzyl 2-amino-6-fluoro-3-pyridinecarboxylate.19. Method of claim 14 wherein the compound is β-methoxyethyl2-amino-6-fluoro-3-pyridinecarboxylate.
 20. Method of claim 14 whereinthe compound is applied preemergently at a rate of 0.10 to 20pounds/acre.
 21. Method of claim 14 wherein the compound is appliedpostemergently at a rate of 0.10 to 20 pounds/acre.